{assign var="through_default" value=$through_default|cat:", category_id"}

<div class="container">
    
    <div class="left">
        {block module="gallery" name="categories" file="gallery/block/backend/categories.tpl"}
    </div>
    
    <div class="right">
        {include file="gallery/backend/photos/list.tpl"}
    </div>
    
    <div class="clear"></div>
</div>
